JPH11150973A - Linear motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a highly reliable linear motor which is provided with a stator having field magnets, and a movable element having armature coils into which the stator is inserted and capable of performing reciprocating movement along the stator, and operates precisely and smoothly. SOLUTION: A linear motor LMa is fitted with a stator 1 having field magnets 11, a movable element 2 having armature coils 21 into which this stator 1 is inserted and capable of reciprocating movement along the stator 1, Hall elements h1 , h2 , h3 (first detecting sensors) which are fitted to the movable element 2 and detect the change of the magnetic information of the scale 31. Here, the Hall elements h1 , h2 , h3 and the MR element 32 are provided in regions excluding a region above the upper surface or the stator 1 out or the peripheral regions or the stator 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a stator having a field magnet in which N-poles and S-poles are alternately arranged and extending in a fixed direction, and an armature coil facing the field magnet. And a mover reciprocally movable along the stator.

[0002]

2. Description of the Related Art Linear motors are used to linearly move articles and members in a wide range of fields, such as OA equipment such as copiers, image scanners and printers, XY tables, FA equipment such as article transporters, and optical equipment such as cameras. It is used to move to. As such a linear motor, an N-pole magnetic pole and an S-pole
A pole having magnetic field magnets arranged alternately, a stator extending in a certain direction, and an armature having an armature coil facing the field magnet and capable of reciprocating along the stator. There is known a so-called moving coil type linear motor provided. In this type of linear motor, the current and the field magnet are formed by passing a current corresponding to the polarity of the magnetic pole of the field magnet facing each coil portion constituting the armature coil. The mover thrust in a desired direction can be generated by interaction with the magnetic field.

A sensor for detecting a change in the magnetic pole of the field magnet is mounted on the mover to control the energization of the armature coil to generate the mover thrust. As a sensor for such a field magnet, a magneto-electric conversion element such as a Hall element or a magneto-resistance element (MR element) that can output an electric signal according to the polarity of a magnetic pole or the strength of a magnetic field is usually employed.

A linear motor usually employs a linear encoder for position detection, speed detection, position control, speed control, etc. of a movable element or a driven body such as an article or member connected to and driven by the movable element. Is done. Linear encoders are broadly classified into magnetic encoders and optical encoders. A magnetic encoder scale in which N magnetic poles and S magnetic poles are alternately arranged in the mover moving direction at a pitch finer than the magnetic pole pitch in the field magnet;
And a magnetic sensor for reading magnetic information of the scale. As such a magnetic sensor, a magneto-electric conversion element such as a magneto-resistive element (MR element) or a Hall element that outputs an electric signal according to the polarity of the magnetic pole of the magnetic encoder scale or the strength of the magnetic field is usually employed.

The optical encoder comprises an optical encoder scale in which two optically different surfaces are alternately arranged in the moving direction of the mover, and an optical sensor for reading optical information of the scale. As such an optical sensor, a photoelectric conversion element such as a photodiode or a phototransistor capable of outputting an electric signal according to the amount of light from an optical scale, or a light emitting diode (LED) that irradiates light to an encoder scale In some cases, a light sensor in which a light emitting element such as described above and a photoelectric conversion element are combined, in other words, a one-packaged optical sensor is used.

[0006]

However, a sensor for detecting a change in the magnetic pole of the field magnet as described above,
Despite the fact that many sensors that read the encoder scale information deteriorate when exposed to heat or have reduced detection accuracy, the sensor that reads the encoder scale information without any consideration of the heat generated by the armature coil Provided and used.

For example, a Hall element, which is a kind of magnetoelectric conversion element that can be employed as a sensor for a field magnet or a sensor for a magnetic encoder, is typically an InSb (indium antimony) -based Hall element, an InAs (indium arsenide) -based Hall element, A GaAs (gallium arsenide) -based Hall element can be cited, but the output varies depending on the ambient temperature, although there is a difference in size. In particular, In
The Sb-based Hall element has a large output signal (Hall voltage), but has poor temperature characteristics, and the output voltage greatly varies depending on the temperature. Further, an MR element, which is a type of magnetoelectric conversion element, has a characteristic that the output decreases as the temperature increases.

Also, the optical sensor employed in the above-described optical encoder may be deteriorated or deteriorated in detection accuracy under the influence of temperature. If the sensor for the field magnet or the sensor for the encoder deteriorates due to temperature or the output fluctuates in this manner, the information to be detected cannot be detected with high accuracy. Inconveniences such as malfunctioning or malfunctioning occur with high accuracy.

Nevertheless, in the conventional linear motor, these sensors are provided without considering the influence of heat generated from the armature coil, and either the sensor for the field magnet or the sensor for the encoder is provided. Even if one happens to be provided at a position where the influence of heat from the armature coil is small (for example, a position below the stator), the other sensor is at a position susceptible to the heat (for example, a position above the stator). ). As described above, when any of the sensors is provided at a position susceptible to the influence of heat from the armature coil, and as a result, the information detection accuracy of the sensor decreases, the linear motor as a whole still does not operate accurately and smoothly. And inconveniences such as malfunction. Such a problem is apt to occur in a so-called shaft type linear motor in which a moving coil type linear motor has an armature coil of a mover which is fitted around a stator.

The moving coil type linear motor, especially the shaft type linear motor, has the following problem in addition to the above-mentioned problem relating to heat generation from the armature coil. One is that a magnetic encoder is adopted, and the magnetic encoder scale may be formed on the stator together with the field magnet, but the magnetic force of the magnetic encoder scale is usually weaker than the magnetic force of the field magnet, Since the type encoder scale receives magnetic interference from the field magnet, and the sensor that reads the magnetic information of the encoder skeleton also receives the influence of the magnetism of the field magnet, the detection accuracy of the encoder scale magnetic information by the sensor is reduced. In some cases, the detection error may occur. If the detection of the encoder scale information is hindered in this way, inconveniences such as the linear motor not operating accurately and smoothly or malfunctioning may occur.

Another is a case where the driven element is driven in a state where the movable element of the linear motor is connected to one end of the driven element to be linearly driven in a predetermined direction in a direction crossing the driving direction. The so-called yawing operation in which the mover swings around an axis orthogonal to both the moving direction and the width direction of the driven body extending in the direction transverse to the moving direction is likely to occur, but when this yawing operation occurs, The positional relationship between the field magnet sensor mounted on the mover and the field magnet, or the encoder sensor's positional relationship with the enterr scale may shift or become unstable, causing the linear motor to lose accuracy. Inconveniences such as poor operation or malfunction may occur.

Accordingly, the present invention has a field magnet in which N magnetic poles and S magnetic poles are alternately arranged, and a stator extending in a certain direction, and a field magnet which is fitted to the stator and is fitted to the field magnet. An object of the present invention is to provide a linear motor having an armature coil facing the movable element and a movable element capable of reciprocating along the stator, and a highly reliable linear motor that operates accurately and smoothly. .

[0013]

According to the present invention, there is provided a stator having a field magnet in which N magnetic poles and S magnetic poles are alternately arranged and extending in a predetermined direction; An armature coil externally fitted to the armature and facing the field magnet, and a movable element capable of reciprocating along the stator;
A first detection sensor provided on the mover for detecting a change in magnetic pole of the field magnet; an encoder scale provided in a reciprocating direction of the mover; and an encoder scale provided on the mover. And a second detection sensor for reading the information of the first and second detection sensors, wherein the first and second detection sensors are provided in a region around the stator except a region above the upper surface of the stator. A linear motor is provided.

In this linear motor, similarly to a conventional moving coil type linear motor, when an armature coil is energized, the mover thrust is generated by the interaction between the current flowing through the armature coil and the magnetic field formed by the field magnet. Occurs and the mover is driven along the stator. The energization control of the armature coil is performed by controlling the information such as the polarity of the magnetic pole of the field magnet and / or the strength of the magnetic field detected by the first detection sensor and the encoder scale detected by the second detection sensor. Based on information from

In this linear motor, the first detection sensor for detecting a change in the magnetic pole of the field magnet and the second detection sensor for reading the information of the encoder scale are both armature coils fitted on the stator. This is provided in a region excluding a region above the upper surface of the stator, which is a region in which heat generated from the heater flows most. Therefore, the first and second detection sensors are less affected by the heat from the armature coil, the information detection accuracy is maintained at a predetermined level, and the linear motor operates accurately and smoothly, and the reliability is improved. Has become high.

The first and second detection sensors can be provided outside the armature coil in order to more reliably avoid the influence of heat from the armature coil. Examples of the first detection sensor include a magnetoelectric conversion element such as a Hall element and a magnetoresistance element. The electric signal output from the magnetoelectric conversion element for the field magnet can be used for controlling the energization of the armature coil. A Hall IC in which a field magnet magnetism conversion element and a field magnet signal processing circuit capable of performing binarization processing may be employed.

The encoder scale may be a magnetic encoder scale or an optical encoder scale.
When a magnetic encoder scale is used, the second detection sensor may be a magnetic sensor that reads magnetic information of the encoder scale. When an optical encoder scale is used, the second detection sensor is What is necessary is just to be an optical sensor which reads the optical information of an encoder scale.

As a magnetic sensor for such a magnetic encoder, for example, a magneto-electric conversion element such as a magneto-resistance element (MR element) or a Hall element can be employed. In addition, as an optical sensor for an optical encoder, a photoelectric conversion element such as a photodiode or a phototransistor, which can output an electric signal corresponding to the amount of light from the optical encoder scale, or an optical sensor for the encoder scale. A light emitting element such as a light emitting diode (LED) for irradiating light and a photoelectric conversion element are combined, in other words, a one-packaged optical sensor or the like can be adopted.

When a magnetic encoder including a magnetic encoder scale and a magnetic sensor for reading its magnetic information is employed as the encoder, the magnetic sensor is easily affected by heat. The linear motor configuration arranged at a position that is hardly affected by heat from the armature coil is particularly preferable.

When a magnetic encoder is employed and a magnetic encoder scale is provided on the stator, the first detection sensor and the second detection sensor for detecting a change in the magnetic pole of the field magnet are used. It is preferable to provide the sensor as far as possible from the sensor. This is because, by doing so, the field magnet and the magnetic encoder scale can be easily provided so as to minimize magnetic interference from the field magnet to the magnetic encoder scale and the magnetic sensor.

When a magnetic encoder is employed and a magnetic encoder scale is provided on the stator, the first and second detection sensors (magnetic sensors) and the positions of the magnetic encoder scale are as follows. It can be mentioned as a representative example. The first sensor faces the field magnet from one side of the stator, and the encoder scale is provided on the stator on a side opposite to the stator. The second detection sensor faces the encoder scale from the opposite side surface of the stator. The first sensor faces the field magnet from the lower surface side of the stator, the encoder scale is provided on the stator on the side surface of the stator, and the second detection sensor is It faces the encoder scale from the side of the stator. The encoder scale is provided on the stator on a lower surface side of the stator, the first sensor faces the field magnet from a lateral surface side of the stator, and the second detection sensor is The lower surface of the stator faces the encoder scale.

The field magnet and the magnetic encoder scale may be attached to the stator body later, or may be formed by magnetizing the magnetizable stator body. In the latter case, the field magnet can be obtained by a driving magnetized portion which is magnetized on a stator main body which can be magnetized such that N-poles and S-poles are alternately arranged.
Further, the magnetic encoder scale is provided with a position detecting magnetizing portion formed by magnetizing the N pole and the S pole with a pitch finer than the magnetic pole pitch of the field magnet on the magnetizable stator body. Obtainable.

By the way, it is preferable that the output of the first detection sensor is as large as possible in order to perform accurate energization control for the armature coil. From this viewpoint, when a magnetic encoder is employed and a magnetic encoder scale is provided on the stator, the following linear motor can be recommended. That is, the field magnet has a region where the strength of the magnetic field by the field magnet is maximum and a region where the magnetic field strength is minimum in a region around the stator other than a region above the upper surface of the stator. The first detection sensor is provided on the mover so as to face the field magnet in a region where the magnetic field strength is maximum, and the magnetic encoder scale is provided with the magnetic field strength. And the second detection sensor is a linear motor provided on the mover so as to face the encoder scale.

Further specific examples of such a linear motor include the following linear motors a) and b). a) The first sensor faces the field magnet from one side of the stator, and the magnetic encoder scale is provided on the stator on a side opposite to the stator. And the second detection sensor faces the encoder scale from the opposite side surface of the stator, and the field magnet controls a maximum magnetic field on the one side surface of the stator. A linear motor that is formed so as to obtain strength and to obtain a minimum magnetic field strength on the opposite side surface. b) The magnetic encoder scale is provided on the stator on the lower surface side of the stator, the first sensor faces the field magnet from the lateral surface side of the stator, and the second sensor Of the stator faces the encoder scale from the lower surface side of the stator, and the field magnet obtains the maximum (substantially maximum) magnetic field strength on each of the two lateral surfaces of the stator. And a linear motor formed so as to obtain a minimum magnetic field strength on the lower surface side.

Note that the first detection sensor may be a linear motor of the following c) and d) if it is not necessary to face the field magnet in a region where the magnetic field strength is maximum. c) The field magnet is formed such that a maximum magnetic field strength is obtained on one side of the stator and a minimum magnetic field strength is obtained on the opposite side. A magnetic encoder scale is formed on the stator on the opposite side surface of the stator, and the first detection sensor faces the field magnet from below the stator, and A linear motor in which the detection sensor of 2 faces the magnetic encoder scale on the opposite side surface. d) The field magnet is formed such that a maximum magnetic field strength is obtained on the upper surface side of the stator and a minimum magnetic field strength is obtained on the lower surface side, and the magnetic encoder scale is fixed. The first detection sensor is formed on the lower surface side of the stator, the first detection sensor faces the field magnet from the side surface of the stator, and the second detection sensor is located below the stator. A linear motor facing the magnetic encoder scale.

In the linear motors c) and d), as in the linear motors a) and b), the first detection sensor and the second detection sensor are not affected by heat from the armature coil. Therefore, the linear motor is located at a position where the linear motor is hardly affected, and accordingly, the operational reliability of the linear motor is improved. Further, the linear motors a), b), c) and d) are
Since the magnetic encoder scale is provided on the stator at a position where the strength of the magnetic field by the field magnet is minimized, the magnetic encoder scale and the field magnet to the second detection sensor facing this are used. Magnetic effect is suppressed, and accordingly, the operation can be performed accurately and smoothly.

The portion having the minimum magnetic field strength by the field magnet may not have a magnetic flux distribution. For example, when a magnetic encoder is employed and a magnetic encoder scale is provided on the stator, the field magnet and the magnetic encoder are used to suppress magnetic interference from the field magnet to the magnetic encoder scale. The scales may be provided apart from each other so that they do not contact each other.

In the linear motor according to the present invention, the movable element may be provided with a substrate on which the first and second detection sensors can be mounted. The following is an example of such a linear motor. (1) The mover includes a substrate disposed outside the armature coil, and the first detection sensor is mounted on the substrate and faces the field magnet from outside the armature coil. A linear motor, wherein the second detection sensor is also mounted on the substrate, and the encoder scale is provided on the substrate at a position facing the second detection sensor.

In this case, the substrate may be provided with one or more circuit units for driving the armature coil by energizing the armature coil. However, it is preferable that the first and second detection sensors be provided on the substrate in an area excluding an area above the circuit section so that the first and second sensors are not easily affected by heat generated by the circuit section. . (2) The mover includes a substrate disposed below the armature coil, and the first detection sensor is mounted on the substrate and faces the field magnet from below the armature coil. A linear motor, wherein the second detection sensor is also mounted on the substrate, and the encoder scale is disposed on the substrate at a position facing the second detection sensor.

In each of the linear motors (1) and (2), the encoder scale can be provided at a position outside the stator. In any of the linear motors (1) and (2), the encoder scale may be a magnetic encoder scale, and the second detection sensor may be a magnetic sensor that reads magnetic information of the encoder scale, or The encoder scale may be an optical encoder scale, and the second detection sensor may be an optical sensor that reads optical information of the encoder scale.

In the linear motors (1) and (2),
The first and second detection sensors are arranged at positions that are hardly affected by heat from the armature coil. In addition, the circuit board may be formed with a circuit pattern for connecting a coil group constituting an armature coil in a predetermined connection state, and the circuit pattern may be used to connect the coil group. .

Any of the above linear motors can be used for linearly driving a driven body in a predetermined direction. In driving the driven body, when the mover is connected to one end of the driven body to be linearly driven in a predetermined direction in a direction crossing the driving direction, the movable element is connected to one end of the first and second detection sensors. Among them, at least the second detection sensor may be arranged on a surface including a cross section perpendicular to the predetermined direction of the movable element passing through the center of the yawing operation of the movable element when the driven body is driven, or in the vicinity thereof. By arranging the second detection sensor on the surface including the cross section of the mover passing through the center of the mover yawing operation or in the vicinity thereof, even if the mover performs the yaw operation, the second detection sensor is normally narrower than the second detection sensor. The positional relationship with the encoder scale having a weaker magnetic force than that of the field magnet is prevented from shifting or becoming unstable, so that the linear motor can be driven accurately and smoothly under the control.

If at least one of the first detection sensors is arranged on or near the surface including such a cross section, the linear motor can be driven more accurately and smoothly under control. A typical example of such a driven body driven on one side is a slider on which an optical component for reading a document image in an image reading device is mounted.

[0034]

Embodiments of the present invention will be described below with reference to the drawings. 1 to 3 show an example of an image reading apparatus equipped with the linear motor according to the present invention. FIG. 1 is a schematic plan view of the device. FIG. 2 is a schematic sectional view taken along line XX shown in FIG. FIG. 3 is a schematic sectional view taken along line YY shown in FIG.

In the image reading apparatus shown in FIGS. 1 to 3, the linear motors according to the present invention are used to drive two sliders on which optical components are mounted, as will be described in detail later. This image reading device has a transparent platen glass GL for mounting a document on the upper portion of the device. A cover CV is provided on the upper part of the platen glass GL so as to be openable and closable. In FIG. 1, the cover CV is not shown. Below the platen glass GL, two sliders, which can move in parallel with the platen glass GL and carry optical components, in order to optically scan a document placed on the platen glass GL. SL1,
SL2 is arranged.

The slider 2 of the linear motor LMb is connected to the slider SL1. Similarly, the slider 2 'of the linear motor LMb is connected to the slider SL2. These linear motors LMa and LMb are linear motors having substantially the same configuration. Each of the movers 2 and 2 ′ is externally fitted to a shaft member 10 parallel to the original table glass GL in which the sliders SL1 and SL2 are moved, and can move along the shaft member 10. Shaft member 10
Are supported at a fixed position by being supported by a support member (not shown), and further have a field magnet. Such a shaft member 10 constitutes a common stator 1 of the two linear motors LMa, LMb. Each of the movers 2, 2 ′ has an armature coil 2 fitted externally to the stator 1.
1, 21 '. Linear motors LMa, LMb
Is a so-called moving coil type linear motor.

When the armature coil 21 of the linear motor LMa is energized, the electric current flowing through the coil 21 and the magnetic field formed by the field magnet formed on the shaft member 10 interact with the movable armature coil 21 having the armature coil 21. The child 2 can be driven along the stator 1. Similarly,
When the armature coil 21 'of the linear motor LMb is energized, the mover 2' can be driven along the stator 1.

The slider SL1 includes, as optical components, an illumination lamp LP for irradiating light on a document placed on the platen glass GL and a slider SL for reflecting light from the document.
And a reflection mirror m1 for guiding the light to the second direction. The illumination lamp LP is a fluorescent lamp in this example. A roller r is provided at the end of the slider SL1 opposite to the end to which the mover 2 is attached. Roller r
Can roll on a plate-like guide member G arranged in parallel with the original table glass GL and the stator 1. By these,
The slider SL1 can move while maintaining its posture.

Reflector mirrors m2 and m3 for guiding image light guided from the reflective mirror m1 on the slider SL1 to the reading unit 8 are provided as optical components on the slider SL2.
Is installed. The slider SL2 is also the same as the slider SL.
1 has a roller r at the same position as that of the roller 1, and can move while maintaining the posture. The reading unit 8 includes a slider S
It has a lens 81 for forming an image of the image light guided from the reflection mirror m3 on L2, and an image pickup device (CCD) 82 for reading the formed image light. It should be noted that an image reading apparatus applicable to an analog copying machine can be provided by providing a reflecting means for guiding light from the mirror m3 to a photoconductor for image formation instead of the unit 8 as described above.

When reading an image of a document placed at a predetermined position on the platen glass GL, the illumination lamp LP on the slider SL1 is turned on, and the sliders SL1, SL
2 are respectively connected to linear motors LMa and LMb.
Thus, the original is driven in parallel with the original platen glass GL to scan the original. The slider SL1 and the slider SL2 are driven so that, for example, their speed ratio is 2: 1. At this time, the light emitted from the illumination lamp LP and reflected by the document is sequentially guided to the reading unit 8 by the mirrors m1, m2, and m3. In the reading unit 8, the reflected light from the original document is
An image is formed on the CCD 82, and original images are sequentially read by the CCD 82.

Next, a linear motor LM connected to each slider to drive the sliders SL1 and SL2.
a and LMb will be described in detail. As described above, since these linear motors are linear motors having substantially the same configuration, the following describes these linear motors by taking the linear motor LMa as an example. FIG.
2 is a schematic plan view showing a cross section of the mover portion of the linear motor LMa. FIG. 5 is a schematic cross-sectional view of the linear motor LMa taken along the line ZZ shown in FIG.

The linear motor LMa shown in FIGS.
Is a so-called shaft type linear motor. The linear motor LMa has the linear rod-shaped shaft member 10 on which the field magnet is formed as described above, and the armature coil 21 fitted on the shaft member 10. The linear motor LMa includes a shaft member 1 on which a field magnet is formed.
0 is a stator arranged at a fixed position, and the armature coils 21
Is a main part of the mover that moves along the stator, that is, a so-called moving coil type linear motor. The linear motor LMa further includes a magnetic encoder scale 31 formed on the shaft member 10. In addition,
Like the field magnet 11, this encoder scale 31 is also common to the linear motors LMa and LMb.

The shaft member 10 is made of a machinable and magnetizable material (for example, Fe-Cr-Co-based metal, manganese aluminum (MnAl)). The cross section of the shaft member 10 is formed in a circular shape, and the surface thereof is formed into a smooth shape. The shaft member 10 is magnetized so as to have a preferably substantially rectangular magnetic flux distribution at an equal pitch along the longitudinal direction as shown in FIG. Thereby, the magnetic poles of the N pole and the S pole have the same magnetic pole width (length in the longitudinal direction of the stator) P along the longitudinal direction of the shaft member 10.
Drive magnetized portions alternately arranged at _m are formed, and this is the field magnet 11.

As shown in FIG. 7, when viewed in a section perpendicular to the longitudinal direction of the stator 1, the field magnet 11 has a magnetic flux distribution M in a magnetic field formed by the field magnet.
B is one side surface of the stator 1 (in the illustrated example, the slider S
L1 is maximum on the side and the minimum is on the opposite side (the side opposite to the slider SL1), in other words, one side of the stator 1 (the slider S in the illustrated example).
The magnetic field is formed such that the maximum magnetic field strength is obtained on the side (L1 side) and the minimum magnetic field strength is obtained on the opposite lateral surface side (opposite to the slider SL1).

The magnetic encoder scale 31
As shown in FIG. 4, FIG. 5, FIG. 7, etc., on the stator 1 on the opposite side of the stator 1 where the strength of the magnetic field of the field magnet 11 is minimum, Are formed along. The magnetic encoder scale 31 is formed by providing a magnetized portion for position detection on the stator 1 with the magnetic poles of N and S poles at a magnetic pole pitch smaller than the magnetic pole pitch of the field magnet 11.

As shown in FIG. 4, the width P _m of each magnetic pole of the field magnet 11 in the longitudinal direction of the stator, in other words, the magnetic pole pitch P _m is 30 mm in this example. The magnetic pole pitch of the magnetic encoder scale is 200 μm in this example. In this example, the armature coil 21 has two sets of coil groups each including three coils of U, V, and W phases.
The first set of coil groups and the second set of coil groups are arranged in the stator longitudinal direction in this order. The first set of coil groups includes coils L _U1 , L _V1 and L _W1 , and is arranged in this order in the longitudinal direction of the stator. The second group of coils is a coil L _U2 ,
L _V2 and L _W2 are arranged in this order in the longitudinal direction of the stator.

Each coil of each set is ring-shaped,
It is arranged so as to fit on the stator 1. These coils are in but this embodiment is not limited to being formed to a width of 1/3 of the pole pitch P _m respectively. Also two coils adjacent the one of these coils, their center positions are staggered by P _m / 3 in the lengthwise direction of the stator. In the present embodiment, each of the coils constituting the armature coil 21 is fixed so that the outer peripheral surface thereof is coated with an adhesive, and is integrated.

The armature coil 21 is fitted around the stator 1
It is built in the hollow portion of the hollow rectangular frame 22 and is supported on the inner peripheral surface of the frame 22. The armature coil 21 and the frame 22 are integrated. The frame 22 is provided at both ends in the stator longitudinal direction with bearings 221 which are fitted to the stator 1 and are slidable. The armature coil 21 and the frame which are integrated by the bearings 221 are provided. 22 can move smoothly along the stator 1. The integrated armature coil 21 and frame 22 constitute the mover 2 of the linear motor LMa.

A Hall element h ₁ , which is a kind of magnetoelectric conversion element capable of outputting an electric signal corresponding to the polarity of the magnetic pole,
h ₂ and h ₃ detect the positional relationship between the coils of the armature coil 21 and the magnetic poles of the field magnet 11 in the longitudinal direction of the stator, and the positions and the polarities of the magnetic poles of the field magnet 11 to which each coil faces. Is provided to energize the coil in accordance with the above.

As shown in FIGS. 4, 5 and 7, each Hall element is located outside the armature coil 21 and in a region where the magnetic field strength of the field magnet 11 is maximum, that is, It faces the field magnet 11 on the side of the slider SL1 and is supported by the inner surface of the frame 22. More specifically, it is located at the position facing the field magnet 11 as described above and at the next position in the longitudinal direction of the stator. That, P in the longitudinal direction of the stator 1, the right side in FIG. 4 from the center of the coil L _{U1 m}
/ 6 Hall elements h ₁ to a position shifted is located.
Similarly, from the center position of the coil L _V1 , P _m /
There is disposed a Hall element h ₂ to 6 shifted position, the Hall element h ₃ at a position shifted P _m / 6 on the right side in FIG. 4 are arranged from the center of the coil L _W1.

The above-mentioned Hall elements are not limited to these, but in this case, InS can provide a large output signal even when the Hall element faces the field magnet 11 from outside the armature coil 21.
This is a b-type Hall element. Also, the frame 22 of the mover 2
, A magnetic sensor 32 is mounted outside the armature coil 21 and at a position facing the encoder scale 31. In this example, the magnetic sensor 32 is an MR element, which is a type of a magnetoresistive element.

The structure of the mover 2 'of the linear motor LMb is the same as the structure of the mover 2, and the mover 2' is also provided with a similar Hall element and encoder sensor which are field magnet sensors. A certain MR element is mounted. FIG. 8 is a schematic block diagram of an electric circuit related to the linear motor LMa. As shown in FIG. 8, each coil of the armature coil 21 is connected in a predetermined connection state and connected to the motor drive control circuit 6. Further, the encoder signal processing circuit 51 that can binarize the output signal from the magnetic sensor (MR element) 32 and the output signals of the Hall elements h ₁ , h ₂ , and h ₃ can be binarized. A field magnet signal processing circuit 52 is provided,
These are also connected to the motor drive control circuit 6. The motor drive control circuit 6 controls energization of the armature coil 21 based on the encoder signal, the field magnet signal, and the like output from the encoder signal processing circuit 51 and the field magnet signal processing circuit 52. Further, a lamp lighting circuit 53 for lighting an illumination lamp LP mounted on the slider SL1 is provided.

The motor drive control circuit 6, encoder signal processing circuit 51, field magnet signal processing circuit 52 and lamp lighting circuit 53 are mounted on one electric circuit board 23. Here, the electric circuit board is arranged outside the mover, but may be mounted on the mover. When such an electric circuit board is mounted on the mover, a Hall element or MR
The element may be mounted on the substrate. However, it is preferable that the Hall element, the MR element, and the like, which are easily affected by heat, are mounted so as to avoid a region above a circuit portion mounted on the substrate, which generates a large amount of heat, or a device provided with a heat sink.

The motor drive control circuit 6 and the lamp lighting circuit 53 are arranged at fixed positions outside the mover 2 and drive the motor based on a command from a system control unit 9 for controlling the entire image reading apparatus. Go, lighting lamp LP
Lights up. System controller 9 outside mover 2
And the circuit formed on the electric circuit board 23 are connected by a harness 71. The harness 71 is connected to the electric circuit board 23 by a pair of male and female connectors 72.

In this example, the following signals are transmitted by the harness 71. One is the electric circuit board 23
And the Hall elements h ₁ , h ₂ , h
_3. The power supply voltage is supplied to the MR element 32. Further, a signal (start / stop signal) indicating that the driving of the motor is started or stopped, a signal indicating the driving direction (driving direction signal), and a reference clock signal are transmitted from the system control unit 9 to the motor control circuit 6. You. Further, a signal (lamp on / off signal) for turning on or off the illumination lamp is transmitted from the system control unit 9 to the lamp lighting circuit 53.

Next, the above circuits on the electric circuit board 23 will be described in order. The first set of U-phase coil L _U1 , V-phase coil L _V1 and W-phase coil L _{W1 of} armature coil 21 and the second set of U-phase coil L _U2 , V-phase coil L _V2 , W-phase coil L
_W2 is connected on the mover 2 or on the substrate 23 as follows. That is, each pair of U-phase coils, V
The phase coils and the W-phase coils are respectively connected in parallel, and the coils connected in parallel are star-connected.

The encoder signal processing circuit 51 is a circuit for binarizing an electric signal output from the MR element 32 and converting it into a digital signal (binary signal). The position detection, speed detection, and drive control of the mover 2 can be performed based on the signals binarized (digitized) by the encoder signal processing circuit 51. In this example, the motor drive control circuit 6 is used for PLL control (phase synchronization control) as described later.

The field magnet signal processing circuit 52 is a circuit for binarizing each electric signal output from the hall elements h ₁ , h ₂ , h ₃ and converting it into a digital signal. In this example, the motor drive control circuit 6 controls the energization of the armature coil 21 based on the field magnet signal binarized (digitized) by the field magnet signal processing circuit 52 as described later.

FIG. 9 is a schematic block diagram showing an example of the internal configuration of the motor drive control circuit 6. The motor drive control circuit 6 includes a PLL control circuit (phase synchronization control circuit) 6
2. It has a compensation circuit section 63 and a conduction control circuit section 64. A reference clock signal having a frequency corresponding to the target speed of the linear motor mover 2 is input from the system control unit 9 to the PLL control circuit unit 62.

The PLL control circuit 62 further includes an MR
The encoder signal output from the element 32 and binarized by the encoder signal processing circuit 51 is fed back as a signal indicating the actual moving speed of the mover 2.
In the PLL control circuit section 62, a signal corresponding to the phase difference between the reference clock signal from the system control section 9 and the encoder signal indicating the moving speed from the encoder signal processing circuit 51 is output to the compensation circuit section 63.

In the compensating circuit 63, lead / lag compensation of the transmission system is performed, and a compensated signal corresponding to the phase difference between the reference clock signal and the moving speed signal is supplied to the conduction control circuit 64.
Is input to The energization control circuit unit 64 outputs a constant current corresponding to the compensated signal based on the field magnet signal output from each Hall element and binarized by the field magnet signal processing circuit. Power is supplied to each coil at the timing shown in FIG. As a result, a current that matches the phases of the reference clock signal corresponding to the target speed and the signal corresponding to the actual moving speed of the mover 2 flows through the coils of each phase. At the desired speed.

FIG. 10 shows the timing of energizing each coil when driving the mover 2 in the left direction in FIG. 4, and FIG. 11 drives the mover 2 in the right direction in FIG. At the time of energization to each coil. When energized at such a timing, each coil has a center position in the longitudinal direction of the stator 1 of the coil,
From the position advanced in the drive direction P _m / 6 from the upstream end of the magnetic pole of the field magnet 11 in the drive direction in this direction, another 2
Until the position where the coil advances in the P _m / 3 driving direction, a constant current in a direction in which the coil generates an electromagnetic force in the driving direction flows according to the polarity of the magnetic pole facing the coil. Therefore, when power is supplied to each coil, all the portions of the coil have magnetic poles of one polarity (N pole or S pole).
(Pole) and does not straddle both the north pole and the south pole. Thus, the current supplied to each coil is not converted into a thrust for driving the mover 2 in the direction opposite to the direction in which the mover 2 is to be driven, but is converted into a thrust for driving the mover 2 in the direction in which the mover 2 is to be driven. Therefore, efficiency is high. Also,
For the same reason, when the mover 2 moves along the stator 1, there is almost no change in the thrust.

Although not shown, the linear motor LMb also includes an electric circuit board including circuits similar to the motor drive control circuit 6, encoder signal processing circuit 51, and field magnet signal processing circuit 52 for the linear motor LMa. The board is connected to the system controller 9 via a harness and a connector, and thus operates in the same manner as the motor LMa based on a command from the system controller 9.

In the linear motor LMa described above, the temperature characteristics of the field magnet sensor are poor, and the InSb-based Hall element h whose output voltage greatly varies depending on the temperature is used.
₁ , h ₂ , and h ₃ are employed, and the MR sensor 32 whose output decreases as the temperature increases as the encoder sensor is employed. However, the heat generated from the armature coil 21 flows most. Since it is arranged on both lateral sides of the stator 1 in a region other than the region above the upper surface of the stator 1 which is a region, since it is further arranged outside the armature coil 21, even if the motor LMa Even when the motor is operated, it is hardly affected by the heat generated by the energization of the armature coil 21. Therefore, the information detection accuracy is maintained at a predetermined level, and the motor L
Ma operates smoothly with high precision and is highly reliable.

As shown in FIG. 7, the Hall element h ₁ ,
h ₂ , h ₃ and the MR element 32 are arranged on opposite sides of the stator 1 with the magnetic encoder scale 31 interposed therebetween.
Are formed on the stator 1 so as to be located in a region where the magnetic field strength of the field magnet 11 is minimum, and the MR element 32
, The magnetic interference from the field magnet 11 to the encoder scale 31 and the MR element 32 is suppressed, and the encoder scale 3 by the MR element 32 is reduced accordingly.
The detection of the magnetic information of No. 1 is performed without error and with high accuracy, whereby the motor LMa operates smoothly and accurately with high reliability.

Further, as shown in FIG.
₁ , h ₂ and h ₃ face the field magnet 11 in a region where the magnetic field strength of the field magnet 11 is maximum,
The output of the Hall element based on the detection of information from the field magnet 11 can be increased, and in this respect, the control of energizing the armature coil 21 can be performed accurately without error, and the operation reliability of the motor LMa is accordingly high. It has become.

Further, since the strength of the magnetic field of the field magnet 11 is maximum on the slider SL1 side,
Is larger on the slider SL1 side with the stator 1 interposed. Therefore, when the slider SL1 is driven by the linear motor LMa, the end of the slider SL1 opposite to the mover connection side tends to move with a delay due to the inertia force of the slider, the running resistance at the end, and the like. , The moment in the direction to correct the delay acts on the mover 2, and as a result, the slider SL1 moves in a correct posture.

The advantages of the linear motor LMa can be obtained for the linear motor LMb. In the linear motor described above, the magnetic flux distribution of the magnetic field formed by the field magnet on the stator and the arrangement of the sensor for the field magnet and the sensor for the encoder are set as shown in FIG. To the settings shown in FIG. 12 to 14 show linear motors LMa.
This shows the setting with a linear motor instead of the linear motor, but the same applies to the linear motor LMb.

In the setting shown in FIG. 12, the field magnet 1
1 is such that the magnetic flux distribution MB in the magnetic field formed thereby becomes maximum on both sides of the stator 1 and becomes minimum on the lower side, in other words, the maximum (substantially on both sides of the stator 1). (A maximum may be obtained) and the lower surface side is magnetized so as to obtain a minimum magnetic field strength. The Hall elements h ₁ , h ₂ , and h ₃ face the field magnet 11 on the side of the stator where the magnetic field strength of the field magnet 11 is maximum, and the magnetic encoder scale 31 controls the magnetic field of the field magnet 11. The stator 1 is formed on the lower surface of the stator where the strength is minimum, and the MR element 32 faces this.

In the setting shown in FIG. 13, the field magnet 1
1 is such that the magnetic flux distribution MB in the magnetic field formed thereby becomes maximum on one side of the stator 1 (the side with the slider SL1) and becomes minimum on the opposite side of the stator, in other words, The stator 1 is magnetized so that a maximum magnetic field strength is obtained on one side surface of the stator 1 and a minimum magnetic field strength is obtained on the opposite side. The Hall elements h ₁ , h ₂ , and h ₃ face the field magnet 11 from below the stator 1, and the magnetic encoder scale 31 contacts the stator 1 on the opposite side where the magnetic field strength of the field magnet 11 is minimized. Formed, and this
The R element 32 is facing.

In the setting shown in FIG. 14, the field magnet 1
1 indicates that the magnetic flux distribution MB in the magnetic field formed by the
It becomes maximum on the top side of the stator 1 and minimum on the bottom side.
In other words, in other words, the maximum magnetic field strength on the upper surface side of the stator 1
So that the minimum magnetic field strength can be obtained on the bottom side.
Magnetically formed. And the Hall element h₁, H_Two, H _Three
Represents the field magnet 11 from one side of the stator 1
The magnetic encoder scale 31 is the field magnet 1
1 is formed on the lower surface side of the stator where the magnetic field strength is minimum.
The MR element 32 faces this.

In any of the settings shown in FIGS. 12 to 14, the Hall elements h ₁ , h ₂ , h ₃ and the MR element 32
Since the armature coil 21 is provided on the mover 2 in a region excluding the region above the upper surface of the stator 1 where heat is most likely to flow, even if the linear motor is operated for a long time, the armature coil 21 The motor is less likely to be affected by the heat generated by energization, so that the motor operates accurately and smoothly, and is highly reliable.

In any of the settings shown in FIGS. 12 to 14, the magnetic encoder scale 31 is provided on the stator 1 in the region of the minimum magnetic field strength of the field magnet 11, and the magnetic scale from the field magnet is The effect is suppressed accordingly, which is advantageous in this respect. In the setting of FIG. 12, the Hall elements h ₁ , h ₂ , and h ₃ are the field magnets 11.
In the region of the maximum magnetic field strength.

In the setting of FIGS. 12 and 14, the MR element 3
2 is provided at a position below the stator which is least affected by heat from the armature coil. FIG.
Is characterized in that the hall elements h ₁ , h ₂ , and h ₃ are provided at a position below the stator where the influence of heat from the armature coil is the least. Further, the setting of FIG. 13 is characterized in that the region of the maximum magnetic field strength of the field magnet 11 is directed to the slider SL1.

In any of the cases shown in FIGS. 12 to 14, the Hall element and the MR element are preferably arranged outside the armature coil in order to more reliably suppress the influence of heat from the armature coil. desirable. Next, FIG.
The linear motor LMc shown in FIG. This linear motor can be used in place of the linear motors LMa and LMb, and can be used for driving the sliders SL1 and SL2 of the image reading device.

The linear motor LMc is a moving coil type shaft type linear motor including the stator 1 and the movable element 20 which is fitted to the stator 1 and is movable. The stator 1 has the same configuration as that of the motor LMa, and forms the field magnet 11 and the magnetic encoder scale 31. The magnetic flux distribution MB of the field magnet 11 is as shown in FIG.

The mover 20 has an armature coil 210 and a mover frame 220 surrounding the armature coil 210 and supports the Hall elements h ₁ , h ₂ , h ₃ and the MR element 32. The mover 20 can smoothly move on the stator by bearings 2210 provided at both ends of the mover frame 220.
The armature coil 210 has two sets of coil groups each including three coils of the U, V, and W phases. The first set of coil groups and the second set of coil groups are arranged in the stator longitudinal direction. Are located in The first set of coil groups includes coils L _U1 ′, L _V1 ′
And L _W1 ′, and are arranged in this order in the longitudinal direction of the stator. The coil group of the second set includes coils L _U2 ′ and L _V2 ′
And L _W2 ′, and are arranged in this order in the longitudinal direction of the stator. Each coil of each set is ring-shaped, and is arranged so as to fit on the stator 1. However, these coils, unlike in the case of linear motors LMa, is formed to a smaller width Pc than the width of 1/3 of the pole pitch P _m respectively. Spacers S are provided between adjacent coils. Also two coils adjacent the one of these coils, their center positions are staggered by P _m / 3 in the lengthwise direction of the stator. These coils constituting the armature coil 210 are fixed together with the spacer S so that their outer peripheral surfaces are coated with an adhesive, and are integrated. The armature coil 210 is
It is externally fitted to the stator 1, is built in the hollow portion of the hollow rectangular frame 220, and is supported on the inner peripheral surface of the frame 220.

The Hall elements h ₁ , h ₂ and h ₃ are shown in FIG.
As shown in (A), the field magnet 11 is applied outside the armature coil 21 and in a region where the magnetic field strength of the field magnet 11 is maximum, that is, on the side of the stator 1 on the side of the slider SL1. And is supported by the inner surface of the frame 220. More specifically, it is located at the position facing the field magnet 11 as described above and at the next position in the longitudinal direction of the stator. That is, in the longitudinal direction of the stator 1, the Hall element h ₁ is shifted to the right side in FIG. 15 by P _m / 6 from the center position of the coil L _U1 ′.
Is arranged. Similarly, the coil L _V1 'is arranged a Hall element h ₂ at a position shifted P _m / 6 to the right in the drawing from the center of the coil L _W1' P _m / 6 shifted right in the figure from the center of Hall elements h ₃ are arranged in positions.

Further, the frame 220 of the mover 20
At the position facing the encoder scale 31, a magnetic sensor (MR
Element 32 is mounted. This is the central spacer S
And is facing the scale 31. MR element 32
Is located inside the armature coil 210,
Since the armature coil is arranged between adjacent coils avoiding the region immediately above the coil, the armature coil is arranged in the same manner as when the MR element is arranged outside the armature coil as in the case of the motor LMa. The effect of heat from the coil is suppressed.

In this linear motor LMc, the Hall element h ₃ and the MR element 32 pass through the center Yc of the yawing operation of the mover 20 and move in the mover moving direction GO (FIG. 15B).
(See FIG. 2). The yawing operation means that the movable element 20 is connected to one end of the slider SL1 or SL2, and when the slider is driven, a running resistance applied to the opposite end of the slider or an inertia force of the slider causes the slider to move. Since the opposite end has a tendency to move later than the end on the mover connection side, the mover 20 is moved in both the mover moving direction GO and the slider width direction WD as shown in FIG. Swinging about an axis Yc perpendicular to
Operation. The axis Yc is the center of yawing.

The motor LMc is operated by the same electric circuit as that of the motor LMa. In the linear motor LMc described above, the same advantages as those already described for the linear motor LMa can be obtained. In the motor LMc Furthermore, the MR element 32 which faces the encoder scale 31 is disposed on a surface Ys passing through the center of yawing operation of the movable element, albeit only one of the three Hall elements, also Hall element h ₃ disposed said surface Ys, Hall element h ₂ is disposed in the vicinity of said surface Ys. Therefore, even if the mover 20 performs a yawing operation, the MR element 32
And the scale 31 and the positional relationship between the Hall elements h ₃ and h ₂ and the field magnet 11 and the instability of the field magnet 11 are suppressed. The linear motor can be driven accurately and smoothly under control.

Next, the linear motors LMd and LMe shown in FIGS. 16 and 18 will be described. These linear motors can be employed instead of the linear motors LMa and LMb.
And SL2. The motor LMd shown in FIG. 16 is a moving coil type shaft linear motor that includes a stator 1d and a movable element 2d that is fitted to the stator and is movable.

The stator 1d is formed by magnetizing a field magnet on a magnetizable shaft member. The magnetic flux distribution of the magnetic field of the field magnet is substantially equal over the entire periphery of the stator cross section. No magnetic encoder scale is formed. Except for this, it is the same as the stator 1 of the motor LMa. The mover 2d has an armature coil 21d and a mover frame 22d surrounding the armature coil 21d. The configuration of the armature coil 21d is the same as that of the armature coil 21 in the motor LMa.

The mover frame 22d includes a slider SL1.
(Or SL2) is open on the side opposite to the side to which it is connected, and the substrate Bd is provided there. 221 in the figure
d is a bearing provided on the frame 22d for sliding along the stator 1d. The substrate Bd has a Hall element h
₁ , h ₂ and h ₃ are mounted, and the electrical positional relationship of these Hall elements with respect to the armature coil 21d is the same as that of the motor LMa. Hall elements h _1, h _2, h
Reference numeral ₃ denotes the stator 1 from outside the armature coil 21d.
d faces the field magnet from the lateral outer side opposite to the slider connection side, and is supported by the inner surface of the substrate Bd.

On the outer surface of the substrate Bd, an optical sensor 42 for an optical encoder is supported at a position just opposite to the Hall element, and an optical sensor extending in the moving direction of the mover at a position facing the optical sensor 41. An encoder scale 41 is provided. At least one of the Hall elements and the optical sensor 42 are connected to the center Y of the yawing operation Ym of the mover 2d.
It is located on or near the plane passing through c.

The linear motor LMd can also be energized and driven by the energization control circuit for the linear motor LMa shown in FIGS. However, in the circuits shown in FIGS. 8 and 9,
The magnetic sensor (MR element) 32 and the encoder signal processing circuit 51 to which the magnetic sensor (MR element) is connected include the optical sensor 42 shown in FIG.
And an encoder signal processing circuit 51 'connected thereto.

On the inner surface of the substrate Bd, a motor drive control circuit 6 and an encoder signal processing circuit 5
1 'and a field magnet signal processing circuit 52 are also mounted. Further, a circuit pattern Lc for star-connecting a coil group forming the armature coil 21d is also mounted. Of the circuit units mounted on the substrate Bd, those that generate heat or are provided with a heat radiating plate are desirably provided at positions where the Hall element or the optical sensor is hardly affected by the heat from these components. The drive control circuit 6 and the circuit pattern Lc are provided above the Hall elements h ₁ , h ₂ , h ₃ and the optical sensor 42, and the other circuit units 5
1 'and 52 are provided on the side of the Hall element and the like.

As shown by a two-dot chain line in FIG. 16, the substrate Bd is slightly extended downward, an optical sensor 42 is provided on the inner surface of the substrate Bd, and an optical encoder scale 41 is installed so as to face this. May be. In this way, a single-sided substrate configuration can be obtained. In any case, the encoder scale 41 has, in this example, light high-reflectance surfaces and light low-reflectance surfaces alternately arranged in the longitudinal direction of the stator. In this example, these two surfaces having different reflectivities are 100 μm.
The stators are arranged at m pitches in the longitudinal direction of the stator. The light sensor 42 here irradiates light toward the encoder scale 41 (a light emitting diode in this example) 421.
And a photodiode 422, which is one of photoelectric conversion elements capable of receiving light emitted from the light emitting element 421 and reflected by the scale 41 and outputting an electric signal according to the light amount. . The encoder signal processing circuit 51 ′ performs a binarization process on the output signal of the photodiode 422.

The motor LMe shown in FIG.
And a movable element 2e which is fitted to the outside and is movable, and is a moving coil type shaft type linear motor. The stator 1e has the same configuration as the stator 1d of the motor shown in FIG. The mover 2e has the same configuration as the mover 2d shown in FIG. However, the mover frame 22e has the slider S
The lower surface orthogonal to the side surface to which L1 (or SL2) is connected is open, and the substrate Be is provided there. In the figure, 221e is a bearing provided on the frame 22e for sliding along the stator 1d.

On the substrate Be, Hall elements h ₁ , h ₂ , h
_3, and the electrical positional relationship of these Hall elements with respect to the armature coil 21e is the same as that of the motor LMa. The hall elements h ₁ , h ₂ , and h ₃ face the field magnet of the stator 1e from below the armature coil 21e, and are supported on the inner surface of the substrate Be. An optical sensor 42 for an optical encoder is supported on the outer surface (lower surface) of the substrate Be at a position just opposite to the Hall element, and an optical sensor extending in the moving direction of the mover at a position facing the optical sensor 41. An encoder scale 41 is provided.

At least one of the Hall elements and the optical sensor 42 are connected to the center Y of the yawing operation Ym of the mover 2e.
It is located on or near the plane passing through c. This linear motor LMe can also be energized and driven by a circuit similar to the energization control circuit for the motor LMd. A circuit pattern Lc for star-connecting a coil group constituting an armature coil is also formed on the inner surface of the substrate Be. However, the motor drive control circuit 6, the encoder signal processing circuit 51 ', and the field magnet The signal processing circuit 52 and the like may be mounted. However, among these circuit parts, those which generate heat or have a heat sink are shown by, for example, a two-dot chain line in FIG. 18 in order to suppress the influence of heat from these on the Hall element and the optical sensor. As described above, the substrate Be may be slightly extended laterally outward, and may be installed at that portion.

The linear motors LMd and LMe described above
However, the Hall elements h ₁ , h ₂ , h ₃ and the optical sensor 42, which may be deteriorated by heat, deteriorate the detection performance, or malfunction, cause the heat generated from the armature coils 21 d, 21 e to flow most. The armature coils 21d and 21e are arranged on the side surfaces and the lower surface side of the stator in the region excluding the upper regions of the stators 1d and 1e, which are moving regions.
The motor LM for a long time
d and LMe are not affected by the heat generated by the armature coils 21d and 21e, and the information detection accuracy is maintained at a predetermined value. As a result, the motors LMd and LMe operate accurately and smoothly. It is expensive.

Since the optical sensor 42 can detect the information of the scale 41 without being affected by the magnetism of the field magnet, for example, the magnetization of the field magnet can be easily and inexpensively performed. On the other hand, the detection accuracy of the scale information by the sensor 42 can be maintained, so that the motors LMd and LMe can operate accurately and smoothly, and have high reliability.

Further, the optical sensor 42 and one of the three Hall elements, but only one of the Hall elements
Since the movable elements 2d and 2e are arranged in the vicinity of the plane passing through the center Yc of the yawing operation of d and 2e, the positional relationship between the sensor 42 and the scale 41 and the Hall element and the The positional relationship with the magnetic magnet 11 is prevented from shifting or becoming unstable, and the linear motor can be driven accurately and smoothly under control.

The optical encoder scale 41 is
Since it is located in a place where the heat from the armature coil is difficult to reach, it can be formed at low cost using resin.
In the linear motors LMd and LMe, a magnetic encoder (for example, the MR element 32 and the magnetic scale 31 described above) may be used instead of the optical encoder (41, 42).

[0096]

As described above, according to the present invention, N
A field magnet in which the magnetic poles of the poles and the magnetic poles of the S pole are alternately arranged, a stator extending in a certain direction, and an armature coil externally fitted to the stator and facing the field magnet, A highly reliable linear motor, which is a linear motor including a movable element that can reciprocate along the stator, operates accurately and smoothly.

[Brief description of the drawings]

FIG. 1 is a schematic plan view of an example of an image reading apparatus equipped with a linear motor according to the present invention.

FIG. 2 is a schematic sectional view of the image reading device taken along line XX shown in FIG.

FIG. 3 is a schematic cross-sectional view of the image reading device taken along line YY shown in FIG.

FIG. 4 is a schematic plan view showing a cross section of a mover portion of an example of the linear motor according to the present invention.

FIG. 5 is a schematic sectional view of the linear motor taken along line ZZ shown in FIG.

FIG. 6 is a diagram showing an example of a magnetic flux distribution in a stator longitudinal direction formed by a field magnet.

FIG. 7 is a diagram showing a magnetic flux distribution of the field magnet as viewed in a cross section perpendicular to the longitudinal direction of the stator.

8 is a block diagram illustrating an example of a circuit for controlling the energization of the linear motor illustrated in FIG. 4;

9 is a circuit block diagram showing a motor drive control circuit portion in the circuit shown in FIG. 8 in more detail.

10 is a diagram showing a relationship between a detection magnetic pole of each Hall element and an energization timing to each coil when the mover of the linear motor in FIG. 4 is driven leftward in FIG.

11 is a diagram showing the relationship between the detection magnetic pole of each Hall element and the energization timing to each coil when the mover of the linear motor in FIG. 4 is driven rightward in FIG.

FIG. 12 is a diagram showing another example of the magnetic flux distribution of the field magnet in the stator and an example of the arrangement of the sensors corresponding thereto.

13 is a diagram showing another example of the arrangement of sensors for the magnetic flux distribution of the field magnet in the stator shown in FIG. 7;

FIG. 14 is a diagram showing still another example of the magnetic flux distribution of the field magnet in the stator and an example of the arrangement of the sensors corresponding thereto.

FIG. 15A is a schematic plan view showing a cross section of a mover portion of still another example of the linear motor according to the present invention, and FIG. 15B is a diagram showing a yawing operation of the mover. .

FIG. 16 is a schematic sectional view of still another example of the linear motor according to the present invention.

FIG. 17 is a block diagram showing an optical sensor and an encoder signal processing circuit used in the linear motor shown in FIG.

FIG. 18 is a schematic sectional view of still another example of the linear motor according to the present invention.

[Explanation of symbols]

LMa, LMb linear motor 1 stator 10 shaft member 11 field magnets 2,2 'armature 21, 21' armature coils 22, 22 'frame 221 bearing 23 electric circuit board h _1, h _2, h ₃ Hall element ( Magnetoelectric conversion element 31 Magnetic encoder scale 32 MR element (magnetic sensor) 51 Encoder signal processing circuit 52 Field magnet signal processing circuit 6 Motor drive control circuit 71 Harness 72 Connector SL1, SL2 Image reading device slider LMc Linear motor 20 Movable Element 210 Armature coil 220 Frame Yc Center of yawing Ys Surface passing through the center of yawing GO Moving element traveling direction WD Slider width direction LMd, LMe Linear motor 1d, 1e Stator 2d, 2e Mover 22d, 22e Frame Bd, Be Substrate 51 ' Encoder signal processing circuit 41 optical encoder scale 42 light sensor 421 emitting element 422 photodiode (photoelectric conversion element) Lc star connecting circuit patterns

Claims (16)

[Claims] 1. A stator having a field magnet in which N-poles and S-poles are alternately arranged and extending in a fixed direction, and an armature externally fitted to the stator and facing the field magnet. A movable element having a coil and capable of reciprocating along the stator; a first detection sensor provided on the movable element for detecting a change in a magnetic pole of the field magnet; and a reciprocating movement of the movable element An encoder scale provided in a direction, and a second detection sensor provided on the mover and reading information on the encoder scale, wherein the first and second detection sensors are located around the stator. Wherein the linear motor is provided in a region excluding a region above the upper surface of the stator. 2. The linear motor according to claim 1, wherein said first and second detection sensors are provided outside said armature coil. 3. The linear motor according to claim 1, wherein said encoder scale is a magnetic encoder scale, and said second detection sensor is a magnetic sensor for reading magnetic information of said encoder scale. 4. The first sensor faces the field magnet from one lateral surface of the stator, and the encoder scale is provided on the stator on a lateral surface opposite to the stator. 4. The linear motor according to claim 3, wherein the second detection sensor faces the encoder scale from the opposite side surface of the stator. 5. 5. The stator according to claim 1, wherein the first sensor faces the field magnet from a lower surface of the stator, and the encoder scale is provided on the stator on a lateral surface of the stator. 4. The linear motor according to claim 3, wherein the second detection sensor faces the encoder scale from a side surface of the stator. 6. The encoder scale is provided on the stator on a lower surface side of the stator, and the first sensor faces the field magnet from a lateral surface side of the stator. 4. The linear motor according to claim 3, wherein the second detection sensor faces the encoder scale from a lower surface of the stator. 7. The field magnet has a region where the strength of the magnetic field by the field magnet is maximum and a region where the magnetic field strength is minimum in a region around the stator other than a region above the upper surface of the stator. The first detection sensor is provided on the mover so as to face the field magnet in a region where the magnetic field strength is maximum, and the magnetic encoder scale is 4. The stator according to claim 3, wherein the stator is formed so as to be located in a region where the magnetic field intensity is minimum, and the second detection sensor is provided on the mover so as to face the encoder scale. Linear motor. 8. The field magnet is formed such that a maximum magnetic field strength is obtained on one side surface of the stator and a minimum magnetic field strength is obtained on the opposite side surface. The linear motor according to claim 4, wherein: 9. The field magnet is formed such that a maximum magnetic field strength is obtained on each of both lateral surfaces of the stator and a minimum magnetic field strength is obtained on the lower surface. Item 7. The linear motor according to Item 6. 10. The armature includes a substrate disposed laterally outside the armature coil, and the first detection sensor is mounted on the substrate and the field magnet is disposed laterally outside the armature coil. 2. The linear motor according to claim 1, wherein the second detection sensor is also mounted on the substrate, and the encoder scale is installed on the substrate at a position facing the second detection sensor. 3. 11. The circuit board according to claim 1, wherein said substrate includes one or more circuit units for driving said armature by energizing said armature coil, and said first and second detection sensors are provided in said circuit unit. 2. The substrate according to claim 1, wherein the substrate is provided in an area other than an upper area.
0 linear motor. 12. The armature includes a substrate disposed below the armature coil, and the first detection sensor is mounted on the substrate and faces the field magnet from below the armature coil. 2. The linear motor according to claim 1, wherein said second detection sensor is also mounted on said substrate, and said encoder scale is arranged on said substrate at a position facing said second detection sensor. 13. A linear motor according to claim 10, wherein said encoder scale is a magnetic encoder scale, and said second detection sensor is a magnetic sensor for reading magnetic information of said encoder scale. 14. The linear motor according to claim 10, wherein said encoder scale is an optical encoder scale, and said second detection sensor is an optical sensor for reading optical information of said encoder scale. 15. The movable element is connected to one end of a driven body to be linearly driven in a predetermined direction in a direction crossing the driving direction, and at least one of the first and second detection sensors. 15. The detection sensor according to claim 1, wherein the detection sensor is disposed on a plane including a cross section perpendicular to the predetermined direction of the movable element that passes through the center of the yawing operation of the movable element when the driven body is driven, or in the vicinity thereof. The linear motor according to any one of the above. 16. A linear motor according to claim 15, wherein said driven member is a slider on which an optical component for reading a document image in an image reading device is mounted.